From 758d7ac6f9c4db1450b46c6efd2f98280e193ca8 Mon Sep 17 00:00:00 2001
From: markster <markster@f38db490-d61c-443f-a65b-d21fe96a405b>
Date: Wed, 5 Jan 2000 08:20:27 +0000
Subject: Version 0.1.2 from FTP

git-svn-id: http://svn.digium.com/svn/asterisk/trunk@169 f38db490-d61c-443f-a65b-d21fe96a405b
---
 codecs/lpc10/ivfilt.c | 118 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100755 codecs/lpc10/ivfilt.c

(limited to 'codecs/lpc10/ivfilt.c')

diff --git a/codecs/lpc10/ivfilt.c b/codecs/lpc10/ivfilt.c
new file mode 100755
index 000000000..93ef4ff01
--- /dev/null
+++ b/codecs/lpc10/ivfilt.c
@@ -0,0 +1,118 @@
+/*
+
+$Log$
+Revision 1.1  2000/01/05 08:20:39  markster
+Version 0.1.2 from FTP
+
+Revision 1.2  2000/01/05 08:20:39  markster
+Some OSS fixes and a few lpc changes to make it actually work
+
+ * Revision 1.1  1996/08/19  22:31:53  jaf
+ * Initial revision
+ *
+
+*/
+
+#ifdef P_R_O_T_O_T_Y_P_E_S
+extern int ivfilt_(real *lpbuf, real *ivbuf, integer *len, integer *nsamp, real *ivrc);
+#endif
+
+/*  -- translated by f2c (version 19951025).
+   You must link the resulting object file with the libraries:
+	-lf2c -lm   (in that order)
+*/
+
+#include "f2c.h"
+
+/* ********************************************************************* */
+
+/* 	IVFILT Version 48 */
+
+/* $Log$
+ * Revision 1.1  2000/01/05 08:20:39  markster
+ * Version 0.1.2 from FTP
+ *
+/* Revision 1.2  2000/01/05 08:20:39  markster
+/* Some OSS fixes and a few lpc changes to make it actually work
+/*
+ * Revision 1.1  1996/08/19  22:31:53  jaf
+ * Initial revision
+ * */
+/* Revision 1.3  1996/03/15  21:36:29  jaf */
+/* Just added a few comments about which array indices of the arguments */
+/* are used, and mentioning that this subroutine has no local state. */
+
+/* Revision 1.2  1996/03/13  00:01:00  jaf */
+/* Comments added explaining that none of the local variables of this */
+/* subroutine need to be saved from one invocation to the next. */
+
+/* Revision 1.1  1996/02/07 14:47:34  jaf */
+/* Initial revision */
+
+
+/* ********************************************************************* */
+
+/*   2nd order inverse filter, speech is decimated 4:1 */
+
+/* Input: */
+/*  LEN    - Length of speech buffers */
+/*  NSAMP  - Number of samples to filter */
+/*  LPBUF  - Low pass filtered speech buffer */
+/*           Indices LEN-NSAMP-7 through LEN read. */
+/* Output: */
+/*  IVBUF  - Inverse filtered speech buffer */
+/*           Indices LEN-NSAMP+1 through LEN written. */
+/*  IVRC   - Inverse filter reflection coefficients (for voicing) */
+/*          Indices 1 and 2 both written (also read, but only after writing).
+*/
+
+/* This subroutine has no local state. */
+
+/* Subroutine */ int ivfilt_(real *lpbuf, real *ivbuf, integer *len, integer *
+	nsamp, real *ivrc)
+{
+    /* System generated locals */
+    integer i__1;
+
+    /* Local variables */
+    integer i__, j, k;
+    real r__[3], pc1, pc2;
+
+/* 	Arguments */
+/*       Local variables that need not be saved */
+/*       Local state */
+/*       None */
+/*  Calculate Autocorrelations */
+    /* Parameter adjustments */
+    --ivbuf;
+    --lpbuf;
+    --ivrc;
+
+    /* Function Body */
+    for (i__ = 1; i__ <= 3; ++i__) {
+	r__[i__ - 1] = 0.f;
+	k = i__ - 1 << 2;
+	i__1 = *len;
+	for (j = (i__ << 2) + *len - *nsamp; j <= i__1; j += 2) {
+	    r__[i__ - 1] += lpbuf[j] * lpbuf[j - k];
+	}
+    }
+/*  Calculate predictor coefficients */
+    pc1 = 0.f;
+    pc2 = 0.f;
+    ivrc[1] = 0.f;
+    ivrc[2] = 0.f;
+    if (r__[0] > 1e-10f) {
+	ivrc[1] = r__[1] / r__[0];
+	ivrc[2] = (r__[2] - ivrc[1] * r__[1]) / (r__[0] - ivrc[1] * r__[1]);
+	pc1 = ivrc[1] - ivrc[1] * ivrc[2];
+	pc2 = ivrc[2];
+    }
+/*  Inverse filter LPBUF into IVBUF */
+    i__1 = *len;
+    for (i__ = *len + 1 - *nsamp; i__ <= i__1; ++i__) {
+	ivbuf[i__] = lpbuf[i__] - pc1 * lpbuf[i__ - 4] - pc2 * lpbuf[i__ - 8];
+    }
+    return 0;
+} /* ivfilt_ */
+
-- 
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